Circuit breaker



Feb. 23, 19430 J. G. JACKSON CIRCUIT BREAKER Filed July 18, .1941 2 Sheets-Sheet 1 Feb. 23, 1943- J, JACKSON 2,312,167

CIRCUIT BREAKER Filed July 18, 1941 2 Sheets-Sheet 2 7 7 57 .4 a: 27 Z5 23 i; /.9 Z1 1 g 7 27 2 Z4, /.9 I

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BY {M ATTORNEY for a greater-movement oi art from the Patented Feb. 23, 1943 omourr BREAKER.

John G. Jackson, Detroit, Mich, assignor to Detroit, Mich, a corpora- Bquare 1) Company, tion of Michigan Application July 181, 1941, Serial No. 403,035 19 Claims. (01. 200-88) This inventionrelates to automatic electric circuit breakers and more'particularly to the current "responsive tripping means for eiiecting the automatic opening of such circuit breakers uponcurrent overload. 7

One object 01' the present invention is to provide a simple and economical but effective com'-" bined thermal and magnetic tripping mean for an "automatic electric circuit breaker.

Another object of this invention is to provide a tripping means for an automatic electric circuit breaker in which the magnetic elements are'providedwith a minimum air gap but with the-armature movement greaterthan this minimum air gap.

Another object of the invention is to provide a current responsive tripping means for an automatic electric circuit breaker including a yoke and movable armature member with the yoke movable relative to-the base so as to provide the armature than is provided by a relatively small air gap between the yoke and armature.

Another object of the invention is to provide a greatly simplified and economical armature mounting arrangement for the current responsive tripping means oi a circuit breaker.

Another object'oi'the invention is to provide a simple and economical latch for the releasable portion of an automatic electric circuit breaker.

Other objects and features of the invention will-be readily apparent to those skilled in the specification and appended drawings illustrating certain preferred embodiments in which: I

Figure l is avertical sectional view oi a iorm oicircuit breaker including the current responsive tripping means of :thepresent' invention.

"Figure 2 is a'detail sectional view on the line nn'or Figure'l: I

j'l igure 3 is adetail sectional view on the line III-III oi Fmlre 1.

ll 'igure 4 is a partial sectional view similar to .gure. l, 'hut showing a modified arrangement for the current responsive tripping means.

l 'igure'5 is a perspective view of elements of ecurrent responsive tripping means according to the present invention.

The present invention has been illustrated in connection with a circuit breaker mechanism which comprises a base I having a conducting strap"! mountedon one end ledge thereof and carrying at its interior-ends. stationary contact 3, the connector! extending through an opening in a iiber plate 4 which closes the end of the 6 base. Exterior of the plate 4 is a terminal connector 8 for the attachment of circuit wiring. Guided ior rectilinear movement within the base is a' generally U-shaped element 6 upon-whose long leg is pivotally mounted, by inter-engaging notches, a contact bar 7 carrying at one end a movable contact 8 cooperating with the stationary contact 3. Fiber plates indicated at 8 combine with the plate 4 to enclose the contacts 3 and 8 within an arcing chamber. An operating handle is provided at H pivotally mounted upon a shaft l2 and having a cam surface I! cooperating with the flat surface of the member 8 to eiIect manual movement oi the contact bar I. A compression spring i4 is disposed between the bottom of the base i and the bar I to bias the same.

Upon the lower end ledge of the base I is mounted a conducting element having disposed thereagainst the terminal connector I8 and extending into the interior of the breaker which is sealed from access by a fiber end plate ll. The interior end of element It is provided with a central pressed out portion II to which is rigidly welded the bimetallic element It. Between the pressed out central portion l8 and the side arms 2i remaining on the connector I! is disposed a bridging element 22 within which is threaded the stud 23 which bears against the pressed out portion is and whose adjustment provides for movement of the bimetallic support and, hence, for adjustment of the position of the bimetal to determine the latching overlap as will be hereinafter described. Embracing the bimetallic element it is a magnetic yoke 24 which may be described as being of generally U shape with side-flanges on its legs and with a portion oi the bight of the U cut away. The side flanges oi the yoke are indicated at 25 in Figure 2 and are mounted within enlarged slots 2' in the side walls of the base so that the yoke is loosely mounted within the base and has a considerable permissible transverse movement. A magnetic armature element 21 is provided which has pressed out side portions 2| adapted to cooperate with the pole pieces formed by the flanges 25 on the yoke 24 to complete the magnetic circuit, the spacing between the pressed out portions 2! and the flanges 25 forming the air gap of the magnetic circuit. The armature 21 is provided with lugs 29 at its pivotal end which are received within notches 3i in the side wall of the base to limit the armature movement to a pivotal one. The actual pivotal support for constructed as follows.

the armature is, however,

A continuous resilient spring member 32 is looped about the pivotal end of the armature and is welded to its opposite sides somewhat adjacent the middle portion of the armature. This provides a looped end portion at 33 in which the adjacent end of the armature freely floats. The breaker is provided with a cover including a metal plate 34 sealed to the base and lined with an insulating fiber plate 35. The looped portion 33 bears against the inner surface of the fiber plate 35 under the bias exerted by the spring I! on the contact arm 1 and this plane and curve bearing, together with the floating armature mounting, provides for the free pivotal move-. ment of the armature to its attracted and un'- attracted positions.

The end of the spring 32 adjacent the bimetal I9 is curved away from the armature as shown at 36 and bears against the bimetal to bias the armature away from the bimetal and the magnetic yoke. The movement of the armature away from the bimetal is limited by the head portion 31 on the smaller bent leg of the bimetal l8, which leg at 38 is reduced in width and received within a notch 39 in the armature 21, whereby the armature may freely swing toward the main body of the bimetal against the bias of the spring 36 and the unattracted position of the armature away from thebimetal is determined by its engagement with the head 31 at the free end of the bimetal.

The opposite end of the spring 32 is biased away from the plane of the armature 21 and then bent at right angles to said plane to form a resilient latching tip 4|. The extreme end of this portion of the spring i provided with a return bent flange at 42 which engages the lower surface of the armature to limit the movement of the latching tip'll away from the plane of the armature. It is this latching tip ll which engages and normally restrains the latching end oi the contact bar I.

The device as shown in full lines in Figure 2 is in its normal operating closed circuit position. The dotted line position of the mechanism indicates the automatic tripped position in which the circuit through the breaker is open upon theHoccuri'ence-of an excess current condition. The breaker is reset in the latched position by manipulation of the operating handle I I and the contacts are moved to their manual on and "oiP positions for normal switching also by manipulation of the handle H, the operation of this mechanism being more fully described in my Patent No. 2,096,546 but with the handle op: eration described in my Patent No. 2,096,545, both issued October 19, 1937.

The operation of the tripping mechanism is as follows:

For low current overloads of continued duration, the bimetal l9 becomes heated and flexes in a clockwise direction to move the armature 21 and the latching tip 4| to disengage the bar I which moves to its automatically tripped position under the bias of spring II as shown in the dotted lines in Figure 1. Upon the occurrence of heavier overloads, the magnetic elements of the trip operate quicker than the thermal flexing action of the bimetal 19 to effect the tripping of the breaker magnetically in a shorter elapsed time than would be taken by the bimetal alone. As nearas can be determined by test of the device, the initial movement of the armature 21 is effected when the yoke 24 is in its position closest to the armature and the flanges 25 are enga n the upper edges of the slots 26. In some instances it may be desirable to bias the yoke into this position by a relatively light spring, but in general, the operation of the device is such that regardless of the position of the yoke, its action to move the armature will be effected when it is in its closest position engaging the bottom edges of the slots 26, the first magnetic action will be to pull the movable yoke up into engagement with the upper edges of the slot; this, because the yoke has less resistance to its movement than does the armature and associated elements. As viewed in Figures 2 and 3, the yoke is shown in this upper attracted position before movement of the armature. With the yoke in this position, a minimum'air gap is provided for the magnetic circuit and'a comparatively greater pull is exerted on the armature. In fact, this air gap may be selected so that if the yoke were positively maintained in this position, the armature would not have sufficient movement to effect unlatching of the contact bar. What apparently happens upon the action of the magnetic elements in tripping the breaker, although applicant does not .wish to be limited to any particular theory of operation, is that the attracted armature'in its movement strikes the yoke 24 and forces it backwards within the slot 26 until a sufiicient travel has been had to effect release of the contact bar and automatic tripping of the breaker. The positioning of the yoke so that it is movable relative to the base permits a constant self-adjusting minimum air gap to be e tablished which may be less than the necessary-a mature travel and permits the forcing back of t e yoke by the moving armature in its attractionto the tripping position so that the initial air gap can be established at a distance less than the effective tripping movement of the armature member. This permits a much greater attraction force for a given current over that which could be obtained with the air gap necessary if the yoke were rigidly emplaced, i a I One important feature of the invention lies in the use of the metal strip to supplya latching surface for the breaker. When the latched elements of, an automatic circuit breaker engage a sheared or punched part or similar elements,- it is necessary for the latching surface oi these parts or elements to be carefully ground, a relatively expensive operation. Hence, one feature of the invention lies broadly in the-use of a formed metal strip as a latching surface. this structure avoiding the necessity for the grinding operation. i Another feature of the invention lies in the resiliency of the latching tip 4! which permits its latching tip to be moved backwardly toward the armature in the resetting movement of thereleasable contact bar. The mounting of the armature in the same pring structure which biases it and supplies the latching surface provides a simple and economical and' frictionless pivotal v mounting for the armature member in which the" rounded loop of the spring bears against the underside of theplate 25 and in which the adjacent end of the armature is fioatingly mounted within The unattracted position ea erness is determined by its engagement; with the head 31. at the end of the bimetal [9; hence, the'adjust-. ment of the bimetal byfthe screw 23 will determine 'the positionv of .the armature. and .the amount of overlap between the latching tip and the releasable contact bar; and, hence, will regulate the thermal calibration of the breaker.

While the tripping of the breaker has been previously described in terms of independent thermal or magnetic effects acting alone, it is apparent that, at least for certain current values.

the tripping will be a combined eiIect in which the thermal flexing action of the bimetal will tend to lessen the initial air gap between the armature and the yoke and will therefore permit action of the magnetic elements at a lower current value.

In the modified form of the invention illustrated in Figure 4, the portion of thespring which is bent to form the latching tip 4| is elongated into the leg 43 and provided with the return flange N which engages the back of a simple bimetal strip 45. A shoulder is provided at I! on the leg which is engaged by the lower armature face to eiIect positive movement of the latching tip in the magnetic operation. Other parts of the tripping unit are the same and the operation of the device is similar to that previously described, with the exception that the force exerted by the bimetal 35 is through the spring element rather than directly on the armature as in the preferred form. This modified point of application of the bimetal flexing force will permit the bimetal 4| to fiex the spring strip to move the latching tip ll toward the armature and release the contact bar in the event that the armature should for any reason bind or otherwise oil'er considerable friction to its movement. While this invention has been described in connection with a particular circuit breaker mechanism to show a complete operative structure in accordance with the patent statutes, it is understood that the tripping means according to the present invention is not limited to any particular mechanism, but may be utilized in many other distinct mechanism forms to which it is adaptable; and, while certain preferred embodiments of the invention have been specifically disclosed, it

is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the artand the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In an automatic electric circuit breaker having separable contacts and means releasable to eflect separation of said contacts, current responsive means for eifecting the release of said releasable means upon the passage or an overload current through the circuit breaker contacts comprising a magnetic yoke, means energizing said yoke in response to current flow through the rircuit breaker, and an armature member movable toward said yoke to effect the release of said releasable means upon the passage of an overload current, said yoke being movably mounted so that the total armature travel is greater than the air gap between said yoke and armature at the instant of initial armature movement.

2. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a magnetic yoke, means energizing said-yoke in response to current fiow through the circuit breaker, and an armature member movable toward said yoke to effect the release of said-releasable means upon the passage oi an overload current, said yoke being mounted for limited transverse movement and having a limiting position toward the armature which provides an air gap less than the distance said armature must move to effect release of said releasable means, the armature in its movement effecting backward movement of the yoke after engaging the same so that the total travel of the armature to efiect release of said releasable means is greater than the minimum air gap before initial armature movement.

3. In an automatic electric circuit breaker having separable contacts and means releasable to eil'ect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a. magnetic yoke, means energizing said yoke in response to current fiow through the circuit breaker, and an armature member movable toward said yoke to eifect the release of said releasable means upon the passage of an overload current, said yoke being mounted for limited transverse movement in the direction of movement of the armature and having a limiting position defining an air gap in the magnetic circuit provided by the yoke and armature which is relatively smaller than the movement oi the armature to eifect release of said releasable means, said armature when attracted continuing its movement after engagement of the yoke to move the yoke backward and provide a sufilcient armature movement to efiect release of said releasable means.

4. In an automatic electric circuit breaker having separable contacts and means releasable to efiect separation of said contacts, current responsive meansfor effecting the release of said releasablemeans upon the passage of an overload current through the circuit breaker contacts comprising a magnetic yoke, means energizing said yoke in response to current flow through the circuit breaker, an armature member movable toward said yoke to effect the release of said releasable means upon the passage of an overload current, said yoke being mounted for limited transverse movement, and means defining a limiting position of the yoke in the direction toward the unattracted position of the armature, which position defines a desired minimum air gap for the magnetic circuit, said yoke ofiering less resistance to at least initial movement than does said armature whereby said yoke will be attracted into said limiting position to provide said desired minimum air gap prior to initial armature movement.

5. In an automatic electric circuit breaker having separable contacts and means releasable to eflect separation of said contacts, current responsive means for efiecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a magnetic yoke, means energizing said yoke in response to current fiow through the circuit breaker, an armature member movable toward said yoke to eil'ect the release of said releasable means upon the passage 01 an overload current, said yoke being mounted for limited trans verse movement, and means defining a limiting position of the yoke in the direction toward the unattracted position of the armature, which position defines a desired minimum air gap for the magnetic circuit, said yoke oilering less resistance to at least initial movement than does said armature whereby said yoke will be attracted into said limiting position to provide said desired minimum air gap prior to initial armature movement, said armature when attracted engaging said yoke and moving it to effect a greater armature travel than would be provided by said minimum air gap if the yoke were rigidly mounted.

6. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a thermally responsive member adapted to be heated in response to the flow, of current through said contacts and flexing in response to heat in a direction to effect release of said releasable means, a magnetic yoke, means energizing said yoke in response to current flow through said contacts, an armature member movable toward said yoke to effect the release of said releasable means, means interconnecting said armature and thermal member so that releasing movement of said thermal member effects movement of the armature in a releasing direction but in which movement of the armature in releasing direction is effected independent of the movement of the thermal member, said yoke being mounted for transverse movement with. a limiting position toward the armature defining a min-- imum normal air gap in the circuit, said armature being capable of moving said yoke away from said limiting position so as to effect a greater armature movement than is provided for by said minimum air gap.

'7. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a bimetallic member adapted to be heated in response to the flow of current through said contacts, a magnetic yoke, an armature member, a magnetic circuit formed by said yoke andsaid armature member embracing a portion of the circuit through said contacts so as to be energized by the current flowing thereplaneoi the major leg of said L shaped bimetal, means pivoting said armature at a point remote from the mailer leg of said L, a tongue and slot connection between the smaller leg of said L and the free end of said armature and an abutment on said tongue limiting the separating movement between said armature and the major leg of said bimetal, means biasing said armature to its maximum separated position with respect to the major leg of said L, and a latching surface on said armature engaging said releasable means, said tongue and slot connection providing for movement of said armature toward the bimetal against said bias whereby releasing movement of the armature in response to magnetic attraction may be effected independent of bimetal movement. H i

9 In an automatic electric circuit breaker having separable contacts and means releasable to eiiect separation of said contacts, currentresponsive means for effecting the release or said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a bimetallic element of substantially L shape, means heating said bimetal in response to current flowing through the circuit breaker, a magnetic yoke, a movable armature, the magnetic circuit formed by said yoke and armature embracing a portion of the circuit through said breaker so as to be energized in response to the flow of current therethrough, said armature extending generally parallel to the plane of the major leg of said L shaped bimetal, means through, a slot in said armature receiving a portion of said bimetallic member in relatively movable relation, an abutment on said portion engageable by said armature to limit their relative movement in one direction, said abutment being so located that movement of the bimetal in a releasing direction effects movement of the armature but movement of the armature in a releasing direction is independent of movement of the bimetal, and means biasing said armature toward a latching position established by its engagement with said abutment on said-bimetal portion. Y

8. In an automatic electric circuit breaker having separable contacts andmeans releasable to effect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a bimetallic element of substantially L shape, means for heating said bimetal in response to current flowing through the circuit breaker, a magnetic yoke, a movable armature, the magnetic circuit formed by said yoke and armature embracing a portion of the circuit through said breaker so as to be energized in response to the flow of current therethrough, said armature extending generally parallel pivoting said armature at a point remote from the smaller leg of said L, a tongue and slot connection between the smaller leg of said L and the free end of said armature and an abutment on said tongue limiting the separating movement between said armature and the major leg of said bimetal, means biasing said armature to its maximum separated position with respect to the major leg of said L, a latching surface on said 31''.- mature engaging said releasable means, said tongue and slot connection providing for movement of said armature toward the bimetal against said bias whereby releasing movement of the armature in response to magnetic attraction may be effected independent of bimetal movement, means mounting said yoke for limited transverse ,movement, means limiting the movement of said yoke in the direction toward the armature to a position providing a normal minimm air gap between the yoke and armature prior to initial armature movement, said armature engaging and moving said yoke after it is magnetically attracted, whereby total armature movement is greater than the minimum air gap thus provided.

10. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a movable member, and a thin metal strip mounted on said member and formed to provide a latching surface which engagessaid releasable means, said member being movable in response to the passage of an overload current through the breaker to effect movement of said latching surface to release said. releasable means, said metallic strip being resilient and self-biasing said latching surface to a definite position with respect to said movable member,

said latching surface being movable relative to.

t the said movable member against its resilient bias.

' diate point and the 11,111 an automatic electric circuit breaker having separable contacts and means releasable to efiect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a member movable in response to current overload, a resilient metal strip mounted on said member and formed to provide a projecting nose on one side of said member, said nose including a flanged flat leg portion transverse to the member, the portion of said leg adjacent said nose forming a latching surface engaged by said releasable means, said member by its inherent resilience biasingsaid nose away from said member and the flange on said leg serving as a limiting stop determining the normal latching position of said nose with respect to said member.

12. Tripping means for effecting automatic opening of an electric circuit breaker in response to the passage of an overload current therethrough comprising a magnetic yoke, means energizing said yoke in response to flow of current through the circuit breaker, an armature member adapted to be attracted to said yoke to effect the release of said releasable means, and a thin metallic strip looped about the pivotal end of said armature member, said loop contacting a fixed part to provide a bearing portion for said armature.

13. Tripping means for eifecting automatic opening of an electric circuit breaker in response to the passage of an overload current therethrough comprising a magnetic yoke, means energizing said yoke in response to the flow of current through the circuit breaker, an armature member adapted to be attracted to said yoke to eflect the release of said releasable means, a thin metaHic strip looped about the pivotal end of said armature member and connected to its opposite faces at points remote to said pivotal end, said loop engaging a fixed part to provide a pivotal mounting and the pivotal end of said armature being freely floating within the loop.

14. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting the release of said releasable means upon the passage of an overload current through the circuit breaker contacts comprising a magnetic yoke, means energizing said yoke in response to current flowing through the circuit breaker, an armature member, a resilient spring strip looped about the pivotal end of said armature and extending toward its free end, one end of said spring strip being formed to provide a latch which restrains said releasable means, the opposite end of said strip engaging abutment means to exert a bias to move said armature toward its unattracted position, the looped end portion of said spring strip engaging a fixed part and absorbing the thrust exerted by said releasable means, said spring being attached to said armature at an intermepivotal end of said armature being freely floating within the looped portion of the spring strip.

15. In an automatic electric circuit breaker I having separable contacts and means releasable to effect separation of said contacts, current responsive means for efiecting the release of said releasable means upon thepassage of an overload current through the circuit breaker contacts comprising a magnetic yoke, means energizing -ture toward its unattracted out said yoke in response to flow of current through the circuit breaker, an armature member movable toward said yoke upon the passage of an overload current through the breaker, a resilient spring strip looped about the pivotal end of said armature and rigidly secured to an intermediate portion thereof, one end of said spring strip being formed to provide a latching surface engageable by said releasable means, the opposite end of said spring strip serving to bias the armaposition, the looped portion of said spring engaging a fixed part to absorb the thrust exerted upon the armature by said releasable means and the pivotal end of said armature being freely floating within said loop.

16. In an automatic electric circuit breaker having separable contactsand means releasable to effect separation of said contacts, current responsive means for effecting release of said releasable means on the passage of an overload current through the circuit breaker comprising a bimetallic member heated in response to the flow of current through the breaker, a magnetic yoke, means energizing said yoke in response to flow of current through the breaker, a movable armature adapted to be attracted to said yoke upon the occurrence of an overload current, means connecting said bimetal to said armature to effect movement thereof upon the flexing of the bimetal when heated, and a thin resilient metal strip mounted on said armature and formed to provide a latching surface engaging said releasable means, said strip engaging said armature adjacent its free end to determine a limiting position of said latching surface with respect to said armature to which it is biased by its inherent resilience.

17. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting release of said releasable means on the passage of an overload current through the circuit breaker comprising a bimetallic member heated in response to the fiow of current through the breaker, a magnetic yoke, means energizing said yoke in response to flow of current through the breaker, an armature member adapted to be attracted to said yoke upon the occurrence of an overload current, means interconnecting said bimetallic element and said armature to effect movement of said armature by said bimetal, a resilient spring strip.looped about the pivotal end of said armature and ex tending toward its free end, one end or" said spring strip being formed to provide a latch which restrains said releasable means, the opposite end of said strip able armature adapted to be attracted by said yoke upon the occurrence of an overload current, a thin metal strip mounted on said armature and formed to provide a latching surface engaged by said releasable means, said strip extending from said armature and engaging said bimetallic member.

19. In an automatic electric circuit breaker having separable contacts and means releasable to effect separation of said contacts, current responsive means for effecting release of said releasable means on the passage of an overload current through the circuit breaker contacts comprising a bimetallic member heated in response to the flow of current through the breaker, a magnetic yoke, means energizing said yoke in response to the flow of current through the breaker, a movable armature adapted to be attracted by said yoke upon the occurrence of an overload current, a resilient metal strip mounted on said armature and formedto provide a latch ing surface engaged by said releasable means, said strip extending from said armature and engaging said bimetallic member, said latching sur-; face being formed by a nose projecting on one side of said armature, which nose includes a flanged fiat leg portion transverse to the armature whose flanges engages with the bimetallic member, and said latching surface being movable with respect to said armature against its resilient bias.

JOHN G. JACKSON. 

